**Abstract**

Modern enology relies on the use of selected yeasts, both *Saccharomyces* and non-conventional, as starters to achieve reliable fermentations. That allows the selection of the right strain for each process and also the improvement of such strain, by traditional methods or approaches involving genetic manipulation. Genetic engineering allows deletion, overexpression and point mutation of endogenous yeast genes with known interesting features in winemaking and the introduction of foreign and novel activities. Besides, it is a powerful tool to understand the molecular mechanisms behind the desirable traits of a good wine strain, as those directed mutations reveal phenotypes of interest. The genetic editing technology called CRISPR-Cas9 allows a fast, easy and non-invasive manipulation of industrial strains that renders cells with no traces of foreign genetic material. Genetic manipulation of non-*Saccharomyces* wine yeasts has been less common, but those new technologies together with the increasing knowledge on the genome of such strains opens a promising field of yeast improvement.

**Keywords:** wine, *Saccharomyces cerevisiae*, non-*Saccharomyces* yeasts, genetically modified organisms, gene editing

### **1. Introduction**

Wine production is a process that happening since the antiquity. For more than 7000 years there has been a continuing evolution in grape juice fermentation and wine production. Humans have used yeasts for wine production without any knowledge about them. Yeast cells were observed for the first time in a microscope in 1680 by Antoine Van Leeuwenhoek. Between 1850 and 1875, Louis Pasteur the role of yeast in alcoholic fermentation for the first time [1]. Grape juice fermentation is a complex microbiological process with a lot of microorganism interactions (yeast, bacteria, filamentous fungi) [2]. *Saccharomyces cerevisiae* has been identifying as the main microorganism responsible of the grape juice fermentation and the bacteria *Oenococcus oeni* as the one for malolactic fermentation that is important for some wines. But in the grape surface there are a lot of species of yeast, while *S. cerevisiae* is hardly found in the vineyard, although is a common resident in winery environments. Non*-Saccharomyces* yeasts contribute to the organoleptic complexity of wine, but are displaced by *Saccharomyces* species that are strong fermenters and are highly tolerant to ethanol [3]. Modern enology relies on the use of starters, generally in the form of active dry yeast (ADY). Select the yeast that you are going to use is

important to have a fast and complete fermentation, decrease lag phase and have a reproducible parameter in the final product [4]. Those starters have been isolated from many environments for their good performance, but they can be further improved by human action by different means.

In this chapter, we focused on the study of the improvement of wine yeast for wine production by recombinant technologies that produce Genetically Modified Organisms (GMOs). That allows a better understanding of the molecular processes relevant for wine yeasts too. We will describe the aspects that have been targeted for improvement, the new technologies of gene editing and synthetic biology and the potential use of these technologies on non-conventional yeasts.
